1. Field of the Invention
The present invention relates to a network device in a packet switched network and more particularly to a method of dynamically allocating color thresholds in a queue to ensure that packets associated with each color are processed in proportion to thresholds defined for other colors.
2. Description of the Related Art
A packet switched network may include one or more network devices, such as a Ethernet switching chip, each of which includes several modules that are used to process information that is transmitted through the device. Specifically, the device includes an ingress module, a Memory Management Unit (MMU) and an egress module. The ingress module includes switching functionality for determining to which destination port a packet should be directed. The MMU is used for storing packet information and performing resource checks. The egress module is used for performing packet modification and for transmitting the packet to at least one appropriate destination port. One of the ports on the device may be a CPU port that enables the device to send and receive information to and from external switching/routing control entities or CPUs.
As packets enter the device from multiple ports, they are forwarded to the ingress module where switching and other processing are performed on the packets. Thereafter, the packets are transmitted to one or more destination ports through the MMU and the egress module. The MMU enables sharing of packet buffer among different ports while providing resource guarantees for every ingress port, egress port and class of service queue. According to a current switching system architecture, packets may be colored based on metering and marking operations that take place in the ingress module and the MMU acts on these packets differently depending on the color of the packet. In a current device, eight class of service queues are associated with each egress port. To ensure bandwidth guarantees across the ports and queues, the device assigns a fixed portion of the bandwidth for the port to each queue and shares unassigned bandwidth between queues that have used their allocated amount. However, the unassigned bandwidth provides a dynamic ceiling for each queue. As such, it is impossible to dynamically process packets in each queue according to predefined proportions assigned to each color.